Skyworks AAT2614 Step-down dc/dc converter with quad high psrr ldo Datasheet

DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
General Description
Features
The AAT2614 is a multiple rail power management IC. It
integrates a 600mA high-frequency switching-converter
and four 300mA linear regulators. The switching power
supply is a highly-integrated monolithic step-down converter operating at 1.7MHz, achieving high efficiency with
small external components. The four linear regulators are
high PSRR low dropout regulators (LDOs) providing accurate regulation and excellent transient response.
• Current Mode Control DC/DC Converter:
▪ Fixed Factory Programmable Output Up to 600mA
▪ 1.7MHz Switching Frequency
▪ Up to 90% Efficiency
▪ Integrated Switching Power FETS
▪ Integrated Compensation Network
▪ Internal Current Limit
•4 Low Dropout Regulators with Separate Enable Pins:
▪ 300mA per Channel
▪ High PSRR
▪ Factory Programmable Output
•Integrated Soft-Start
•Over-Current Protection
•Over-Thermal Protection
•TQFN33-20 and WLCSP-16 Packages
The step-down converter and the four LDOs are all fixed
voltage outputs of seven combinations for 1V, 1.2V, 1.3V,
1.8V, 2.8V, 3.0V and 3.3V. Integrated over-current or
over-temperature protection circuitry becomes active
when overload or over-temperature fault occurs and the
AAT2614 recovers automatically when the fault is
removed.
The AAT2614 is available in a Pb-free, thermally enhanced
20-pin TQFN33 package and a 16-bump 0.4 pitch CSP
package.
Applications
•
•
•
•
•
Cellular Phones
I/O Power
Memory Power
Processor Core Power
Smart Handheld Devices
Typical Application
2.5V to 5.5V
2.2μF
INL1
2.5V to 5.5V
2.2μF
INL2
OUTL1
1μF
OUTL2
1μF
AAT2614-2
ENL1
ENL2
ENL3
ENL4
OUTL3
OUTL4
2.5V to 5.5V
4.7μF
INB
LX
OUTB
AGND PGND
2.8V
300mA
2.8V
1μF 300mA
2.8V
300mA
1μF
2.2μH
ENB
1.8V
300mA
1.2V, 600mA
10μF
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202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
1
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Pin Descriptions
Pin Number
TQFN33-20
WLCSP-16
Symbol
Function
1
C3
INL1
I/O
2
D3
ENL1
I
3
B2
ENL2
I
4
C2
INB
I
5
D2
LX
I/O
6,8,10
7
D1
C1
PGND
ENB
I/O
I
9
B1
OUTB
O
11
A1
ENL3
I
12
A2
ENL4
I
13,17
14
15
B4
A3
B3
AGND
OUTL4
OUTL3
I/O
O
O
16
A4
INL2
I/O
18
19
20
EP
N/C
C4
D4
N/C
N/C
OUTL1
OUTL2
GND
O
O
Description
Power input for LDO1/2. Connect a 2.2μF capacitor between this pin and
ground.
Active high enable pin. When pulled high, LDO1 regulates its output to the
programmed voltage value.
Active high enable pin. When pulled high, LDO2 regulates its output to the
programmed voltage value.
Power input pin for the switching converter. Connect a 4.7μF capacitor between ground and INB.
DC/DC step-down converter switching node. Connect LX to the terminal of
the inductor.
DC/DC converter power ground.
Active high step-down DC/DC converter enable pin.
DC/DC converter output pin. Connect OUTB to a 10μF capacitor connected to
ground.
Active high enable pin. When pulled high, LDO3 regulates its output to the
programmed voltage value.
Active high enable pin. When pulled high, LDO4 regulates its output to the
programmed voltage value.
Analog ground.
LDO4 output. Connect a 1μF capacitor between the pin and ground.
LDO3 output. Connect a 1μF capacitor between the pin and ground.
Power input for LDO3/4. Connect a 2.2μF capacitor between the pin and
ground.
Not connected.
LDO1 output. Connect a 1μF capacitor between the pin and ground.
LDO2 output. Connect a 1μF capacitor between the pin and ground.
Exposed pad.
Pin Configuration
TQFN33-20
(Top View)
WLCSP-16
(Top View)
INL2
AGND
N/C
OUTL1
OUTL2
20
INL1
ENL1
ENL2
INB
LX
19
18
17
15
2
14
3
13
4
12
5
11
7
8
9
3
4
A
OUTL2
OUTL1
AGND
INL2
OUTL3
OUTL4
AGND
ENL4
ENL3
B
ENL1
INL1
OUTL3
OUTL4
C
LX
INB
ENL2
ENL4
D
PGND
ENB
OUTB
ENL3
10
PGND
OUTB
PGND
ENB
PGND
2
2
16
1
6
1
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Absolute Maximum Ratings1
Symbol
Description
Value
INL1, INL2, INB, OUTL1, OUTL2, OUTL3, OUTL4
ENL1, ENL2, ENL3, ENL4
ENB, OUTB
LX to PGND
PGND to AGND, AGND to AGND
Operating Temperature Range
Storage Temperature Range
Maximum Soldering Temperature (at leads, 10 sec.)
TA
TS
TLEAD
-0.3 to 6.0
-0.3 to 6.0
-0.3 to VINB
-0.3 to VINB
-0.3 to +0.3
-40 to 150
-65 to 150
300
Units
V
°C
Thermal Information3
Symbol
Description
ΘJA
Thermal Resistance4
PD
Maximum Power Dissipation
Value
TQFN33-20
WLCSP-16
TQFN33-20
WLCSP-16
50
90.4
2
1.1
Units
°C/W
W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied.
2. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Thermal Resistance measured with the device on multi-layer evaluation board in a thermal oven. The amount of power dissipation which will cause the thermal shutdown to
activate will depend on the ambient temperature and the PC board layout ability to dissipate the heat. De-rate 30mW/°C above 70°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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3
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Electrical Characteristics1
VINB = VINL1 = VINL2 = 3.6V, L = 2.2μH, CINL1, 2 = 2.2μF, CINB = 4.7μF, COUTB = 10μF, VINLx = VOUTLx +0.7V, VENLx = VINLx , COUL1,
o
2, 3, 4 = 1μF, TA= 25 C unless otherwise noted.
Symbol
Description
Conditions
Min
PMU Operation
VIN
Input Voltage
UVLO
TSD
Under-Voltage Lockout
Thermal Shutdown
Quiescent Current
IQ
Logic Control
VIH
Input Logic High Threshold
VIL
Input Logic Low Threshold
DC-DC Step-Down Converter
Shutdown Current from INB Pin
ISHDN
IQ
Quiescent Current
ILIM
P-Channel Current Limit
VOUT_ACC
Output Voltage Accuracy
FSW
Operating Switching Frequency
RDS(ON)H
High-Side Switch On Resistance
RDS(ON)L
Low-Side Switch On Resistance
LDO
ISHDN
ILIM
VDROP
VOUTL_ACC
ΔVOUTL/
IOUTL
VOUTL/
VINL
2.5
Rising
Hysteresis
Threshold
Hysteresis
VENB > 1.5V, VENL1,2,3,4 >1.5V, no load
IOUTB
IOUTB
IOUTB
IOUTB
=
=
=
=
4
800
-3
200mA
200mA, VINB = 2.5V
200mA
200mA, VINB = 2.5V
VENB = VENL < 0.4V
RLOAD = 1Ω
IOUTL = 300mA
TA = -40°C to 85°C, 1mA load
Load Regulation
1mA < IOUTL < 300mA
Line Regulation
VINL1 = VINL2 = 2.7V to 5.5V
Output Voltage Temperature
Coefficient
0.1
120
COUT1,2,3,4 = 1μF,
VINL = VOUTL1,2,3,4 + 1V
Max
Units
5.5
420
V
V
mV
°C
°C
μA
VINB
0.4
V
V
1
280
μA
μA
mA
%
MHz
3
1.7
230
280
180
220
500
-3
0.3
f = 1kHz
f = 10kHz
VOUTL_TC
1.5
VENB < 0.4V, VENL 1, 2, 3, 4 < 0.4V
VENL 1, 2, 3, 4 < 0.4V , VENB >1.5V , IOUTB = 0mA
VINB = 2.7V to 5.5V
TA = -40°C to 85°C, 20mA load
Shutdown Current
Output Current Limit
Dropout Voltage
Output Voltage Accuracy
Power Supply Rejection Ratio
1.9
100
140
15
260
ENL1, ENL2, ENL3, ENL4, ENB
ENL1, ENL2, ENL3, ENL4, ENB
f = 100Hz
PSRR
Typ
IOUT = 10mA
IOUT = 150mA
IOUT = 10mA
IOUT = 150mA
IOUT = 10mA
IOUT = 150mA
mΩ
mΩ
1
600
500
3
μA
mA
mV
%
0.6
%
0.2
%/V
75
75
70
70
50
50
dB
100
ppm/°C
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Supply Current vs. Supply Voltage
Buck Quiescent Current vs. Supply Voltage
(VENB, VENL > 1.5V)
(VOUTB = 1.2V, VENB > 1.5V, VENL < 0.4V)
300
140
280
130
260
120
IQ (µA)
Supply Current (µA)
Typical Characteristics−Step-Down (Buck) Converter
240
85°C
25°C
-40°C
220
110
85°C
25°C
-40°C
100
90
200
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
Supply Voltage (V)
Switching Frequency vs. Temperature
Switching Frequency (MHz)
Switching Frequency (MHz)
1.72
1.70
1.68
1.66
1.64
1.62
10
5.0
5.5
(VOUTB = 1.2V, IOUTB = 600mA)
1.74
-15
4.5
Switching Frequency vs. Input Voltage
(VINB = 3.6V, IOUT = 600mA)
1.60
-40
4.0
Supply Voltage (V)
35
60
85
1.74
1.72
1.70
1.68
1.66
1.64
2.5
3.0
Temperature (°C)
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Buck Efficiency vs. Output Current
UVLO Voltage vs. Temperature
(VOUT = 1.2V; L = 2.2µH)
100
1.95
90
1.91
70
60
50
40
VIN = 2.5V
VIN = 3.6V
VIN = 4.2V
VIN = 5.0V
VIN = 5.5V
30
20
10
0
0.1
1
10
100
Output Current (mA)
1000
VEOC (V)
Efficiency (%)
80
1.87
1.83
1.79
1.75
-40
UVLO_H
UVLO_L
-15
10
35
60
85
Temperature (°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
5
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Typical Characteristics−Step-Down (Buck) Converter
Buck Output Voltage vs. Temperature
Buck Line Regulation
(VINB = 3.6V, IOUT = 600mA)
(VOUTB = 1.2V, L = 2.2µH)
1
1.0
IOUTB = 10mA
IOUTB = 100mA
IOUTB = 300mA
IOUTB = 600mA
Output Error (%/V)
0.8
VOUT Error (%)
0.6
0.2
-0.2
-0.6
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
-40
-15
10
35
60
-1
2.5
85
3.0
Temperature (°C)
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Buck Load Regulation
EN VIH vs. Supply Voltage
(VINB = 3.6V; VOUTB = 1.2V; L = 2.2µH)
1
1.20
1.10
0.6
0.4
EN VIH (V)
Output Error (%)
0.8
0.2
0
-0.2
-0.4
1.00
0.90
85°C
25°C
-40°C
0.80
-0.6
-0.8
-1
10
70
130
190
250
310
370
430
490
550
610
0.70
2.5
3.0
Output Current (mA)
3.5
4.0
4.5
5.0
Supply Voltage (V)
Soft Start
EN VIL vs. Supply Voltage
(VINB = 3.6V; VOUTB = 1.2V; IOUTB = 600mA)
1.2
EN VIL (V)
1.1
VENB
(2V/div)
1.0
0
0.9
VOUTB
(1V/div) 0
0.8
85°C
25°C
-40°C
0.7
0.6
2.5
3.0
3.5
4.0
4.5
Supply Voltage (V)
6
5.0
IINB
(0.2A/div)
0
5.5
Time (40µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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5.5
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Typical Characteristics−Step-Down (Buck) Converter
Buck Load Transient
Buck Line Transient
(VIN = 3.6V; VOUTB = 1.2V; CINB = 10µF; COUTB = 10µF)
(VINB = 4V to 5V; CINB = 10µF; IOUTB = 600mA)
VOUTB
(200mV/div)
1.2
600mA
IOUTB
(200mA/div)
VINB
(1V/div)
4
VOUTB
(100mV/div)
1.2
400mA
0A
Time (40µs/div)
Time (40µs/div)
Output Ripple
(VIN = 3.6V; VOUT = 1.2V; IOUT = 600mA; CINB = 4.7µF)
VOUT1.2
(20mV/div)
VLX
(2V/div)
0
Time (0.4µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
7
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Typical Characteristics−LDO Regulators
LDO Output Voltage vs. Temperature
LDO Quiescent Current vs. Supply Voltage
(Single Channel)
34
0.6
LDO1
LDO2
LDO3
LDO4
0.2
32
IQ (µA)
VOUT Error (%)
0.4
0.0
30
28
-0.2
85°C
25°C
-40°C
26
-0.4
-0.6
-40
-15
10
35
60
24
2.5
85
3.0
3.5
4.5
LDO Line Regulation
5.5
Dropout Voltage vs. Load Current
(VOUTL = 1.8V)
(VOUT = 2.8V)
350
0.2
Dropout Voltage (mV)
0.16
0.12
0.08
0.04
0
-0.04
IOUTB = 10mA
IOUTB = 100mA
IOUTB = 300mA
IOUTB = 600mA
-0.08
-0.12
-0.16
-0.2
2.5
3.0
3.5
4.0
4.5
5.0
5.5
300
250
200
150
100
85°C
25°C
-40°C
50
0
20
60
Input Voltage (V)
100
140
180
220
260
Load Current (mA)
LDO Load Transient
LDO Line Transient
(VIN = 3.6V; VOUTL = 1.8V; CINL = 2.2µF; COUTL = 1µF)
(VINB = 4V to 5V; IOUTL = 300mA)
VOUTL
(200mV/div)
1.8
VINL
(1V/div)
4
VOUTL
(100mV/div)
1.2
300mA
IOUTL
(200mA/div)
0A
10mA
Time (100µs/div)
8
5.0
Supply Voltage (V)
Temperature (°C)
Output Error (%/V)
4.0
Time (40µs/div)
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300
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Typical Characteristics−LDO Regulators
LDO Power Supply Rejection Ratio, PSRR
(IOUT1 = 10mA, BW = 100~100KHz)
100
Magnitude (dB)
90
80
70
60
50
40
30
20
10
0
1.00E+02
1.00E+03
1.00E+04
1.00E+05
Frequency (Hz)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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9
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Block Diagram
INB 4.7μF
Buck
ENB
INL2
2.2μH
1.2V, 600mA
P
LX
Control
10μF
PGND
2.2μF
P
A
P
OUTB
INL1
2.2μF
A
ENL4
Bias, Control, and OTP
Thermal Shutdown
LDO 4
1.8V
300mA
1μF
OUTL4
A
ENL3
LDO 3
2.8V
300mA
1μF
OUTL3
A
ENL2
LDO 2
2.8V
300mA
1μF
OUTL 2
A
LDO 1
2.8V
300mA
1μF
OUTL 1
ENL1
A
AGND
Functional Description
The AAT2614 is a compact power management solution.
It integrates a step-down converter with four high PSRR
low-dropout regulators to provide power from a wall
adapter, USB port, or a single-cell Lithium Ion/Polymer
battery or dual cell alkaline battery.
The AAT2614 uses fixed-frequency peak current control
architecture. Light load mode is used to enhance light
load efficiency. Compensation is integrated to reduce the
10
number of external components and achieve excellent
transient response and load and line regulation.
The ideal 1.7MHz switching frequency allows the use of
smaller output filter components for improved power
density, reduced external component size, and optimized
output voltage ripple.
The AAT2614 has five separate enable pins to control
buck converter and four LDO regulator outputs’ startup.
Also see the “Enable Function” section in the Applications
Information section of this datasheet.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Synchronous Step-Down Converter
Soft-Start
The AAT2614 contains one high performance 600mA,
1.7MHz synchronous step-down converter. The stepdown converter operates to ensure high efficiency performance over all load conditions.
Soft start increases the inductor current limit point linearly when the input voltage or enable input is applied.
It limits the current surge seen at the input and eliminates output voltage overshoot.
The input voltage range is from 2.5V to 5.5V, and the
output voltage is fixed and can be trimmed as shown in
the Ordering Information section of this datasheet.
Power devices are sized for 600mA current capability
while maintaining over 85% efficiency at full load. High
efficiency is maintained at lower currents
Current Limit and
Over-Temperature Protection
A high DC gain error amplifier with internal compensation controls the output. It provides excellent transient
response and load/line regulation. The converter has soft
start control to limit inrush current.
Apart from the input capacitor, only a small L-C filter is
required at the output side for the step-down converter
to operate properly. Typically, a 2.2μH inductor and a
10μF ceramic capacitor are recommended for low output
voltage ripple and small component size.
Control Loop
The converter is a peak current mode step-down converter. The inner, wide bandwidth loop controls the
inductor peak current. The inductor current is sensed
through the P-channel MOSFET (high side) and is also
used for short circuit and overload protection. A fixed
slope compensation signal is added to the sensed current to maintain stability for duty cycles greater than
50%. The peak current mode loop appears as a voltage
programmed current source in parallel with the output
capacitor. The output of the voltage error amplifier programs the current mode loop for the necessary peak
inductor current to force a constant output voltage for all
load and line conditions. The voltage feedback resistive
divider is internal and the error amplifier reference voltage is 0.6V. The voltage loop has a high DC gain making
for excellent DC load and line regulation. The internal
voltage loop compensation is located at the output of the
transconductance voltage error amplifier.
For overload conditions the peak input current is limited.
As load impedance decreases and the output voltage
falls closer to zero, more power is dissipated internally,
raising the device temperature. Thermal protection completely disables switching when internal dissipation
becomes excessive, protecting the device from damage.
The junction over-temperature threshold is 140°C with
15°C of hysteresis.
LDO Regulator
The advanced circuit design of the linear regulator is
specifically optimized for very fast start-up and shutdown timing. This proprietary LDO is also tailored for
superior transient response characteristics. These traits
are particularly important for applications which require
fast power supply timing.
The high-speed turn-on capability is enabled through the
implementation of a fast start control circuit, which
accelerates the power up behavior of fundamental control and feedback circuits within the LDO regulator. Fast
turn-off time response is achieved by an active output
pull down circuit, which is enabled when the LDO regulator is placed in the shutdown mode. This active fast
shutdown circuit has no adverse effect on normal device
operation. The LDO regulator output has been specifically optimized to function with low cost, low ESR ceramic capacitors. However, the design will allow for operation
over a wide range of capacitor types.
The regulator comes with complete short circuit and thermal protection. The combination of these two internal
protection circuits gives a comprehensive safety system
to guard against extreme adverse operating conditions.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202209B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
11
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Application Information
Step-down Converter
Input Capacitor
Select a 4.7uF to 10uF X7R or X5R ceramic capacitor for
the input. To estimate the required input capacitor size,
determine the acceptable input ripple voltage level (Vpp)
and solve for C. The calculated value varies with input
voltage and is a maximum when VIN is double the output
voltage.
CIN =
V
VO
· 1- O
VIN
VIN
VPP
- ESR · fS
IO
VO
D= V
IN
CIN(MIN) =
1
VPP
- ESR · 4 · fS
IO
Where CIN is the input capacitance, VIN is the input voltage, VO is the output voltage, fS is the switching frequency, IO is the output current, ESR is the equivalent series
resistor of output capacitor, and D is the duty cycle.
The maximum input capacitor RMS current is:
IRMS = IO ·
VO
V
· 1- O
VIN
VIN
The input capacitor RMS ripple current varies with the
input and output voltage and will always be less than or
equal to half of the total DC load current.
IRMS =
IO
2
The maximum input voltage ripple also appears at 50%
duty cycle.
The input capacitor provides a low impedance loop for the
edges of pulsed current drawn by the AAT2614. Low ESR/
ESL X7R and X5R ceramic capacitors are ideal for this
function. To minimize parasitic inductances, the capacitor
should be placed as closely as possible to the IC. This
keeps the high frequency content of the input current
localized, minimizing EMI and input voltage ripple.
12
The proper placement of the input capacitors (C1, C2,
and C3) is shown in the evaluation board layout in Figure
2.
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the evaluation board input voltage pins. The inductance of these
wires, along with the low-ESR ceramic input capacitor,
can create a high Q network that may affect converter
performance. This problem often becomes apparent in
the form of excessive ringing in the output voltage during load transients. Errors can also result in the loop
phase and gain measurements. Since the inductance of
a short PCB trace feeding the input voltage is significantly lower than the power leads from the bench power
supply, most applications do not exhibit this problem.
In applications where the input power source lead inductance cannot be reduced to a level that does not affect
the converter performance, a high ESR tantalum or aluminum electrolytic capacitor should be placed in parallel
with the low ESR/ESL bypass ceramic capacitor. This
dampens the high Q network and stabilizes the system.
Output Capacitor
The output capacitor limits the output ripple and provides holdup during large load transitions. A typical
4.7μF X5R or X7R ceramic capacitor typically provides
sufficient bulk capacitance to stabilize the output during
large load transitions and has the ESR and ESL characteristics necessary for low output ripple.
The output voltage droop due to a load transient is dominated by the capacitance of the ceramic output capacitor.
During a step increase in load current, the ceramic output
capacitor alone supplies the load current until the loop
responds. Within two or three switching cycles, the loop
responds and the inductor current increases to match the
load current demand. The relationship of the output voltage droop during the three switching cycles to the output
capacitance can be estimated by:
COUT =
3 · ΔILOAD
VDROOP · fS
Once the average inductor current increases to the DC
load level, the output voltage recovers. The above equation establishes a limit on the minimum value for the
output capacitor with respect to load transients.
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DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Output Inductor
For most designs, the AAT2614 operates with inductor
values of 1.0μH to 4.7μH. Inductors with low inductance
values are physically smaller but generate higher inductor current ripple leading to higher output voltage ripple.
The inductor value can be derived from the following
equation:
L=
VOUT · (VIN - VOUT)
VIN · ∆IL · fOSC
Where ΔIL is inductor ripple current. Large value inductors result in lower ripple current and small value inductors result in high ripple current. Choose inductor ripple
current approximately 30% of the maximum load current 0.6A, or
∆IL = 180mA
Manufacturer’s specifications list both the inductor DC
current rating, which is a thermal limitation, and the
peak current rating, which is determined by the saturation characteristics. The inductor should not show any
appreciable saturation under normal load conditions.
The DC current rating of the inductor should be at least
equal to the maximum load current plus half the inductor ripple current to prevent core saturation (0.6A +
180mA).
Some inductors may meet the peak and average current
ratings yet result in excessive losses due to a high DCR.
Always consider the losses associated with the DCR and
its effect on the total converter efficiency when selecting
an inductor.
Thermal Calculations
There are three types of losses associated with the
AAT2614 step-down converters: switching losses, conduction losses, and quiescent current losses. Conduction
losses are associated with the RDS(ON) characteristics of the
power output switching devices. Switching losses are
dominated by the gate charge of the power output
switching devices. At full load, with continuous conduction
mode (CCM), a simplified form of the losses is given by:
VO
VO
PBUCK = IO2 · RDS(ON)P · V + RDS(ON)N · 1 - V
IN
IN
+ tSW · fS · IO · VIN + IQ · VIN
Where IQ is the step-down converter quiescent current,
tsw is the switching time, RDS(ON)P and RDS(ON)N are the high
side and low side switching MOSFETs’ on-resistance. VIN,
VO and IO are the input voltage, the output voltage and
the load current.
Since RDS(ON), quiescent current and switching losses all
vary with input voltage, the total losses should be investigated over the complete input voltage range.
Given the total losses, the maximum junction temperature can be derived from the θJA for the package.
TJ(MAX) = PTOTAL · θJA + TA
Enable Function
The AAT2614 features one buck output enable/disable
function for buck converter. This pin (ENB) is active high
and is compatible with CMOS logic. To assure the buck
output will switch on, the ENB turn-on control level must
be greater than 2.4V. The buck converter will go into the
disable shutdown mode when the voltage on the ENB pin
falls below 0.6V. If the enable function is not needed in
a specific application, it may be tied to VIN to keep the
buck output in a continuously on state.
Low Dropout Regulator
Input Capacitor
Typically, a 2.2μF or larger capacitor is recommended for
CIN in most applications. A CIN capacitor is not required
for basic LDO regulator operation. However, if the LDO is
physically located any distance more than one or two
centimeters from the input power source, a CIN capacitor
will be needed for stable operation. CIN should be located
as closely to the device VINL pin as practically possible.
CIN values greater than 1μF will offer superior input line
transient response and will assist in maximizing the
power supply ripple rejection.
Ceramic, tantalum, or aluminum electrolytic capacitors
may be selected for CIN as there is no specific capacitor
ESR requirement. For better performance, ceramic
capacitors are recommended for CIN due to their inherent capability over tantalum capacitors to withstand
input current surges from low impedance sources such
as batteries in portable devices.
Output Capacitor
For proper load voltage regulation and operational stability, a capacitor is required between pins VOUT and GND.
The COUT capacitor connection to the LDO regulator
ground pin should be made as direct as practically possible for maximum device performance. The AAT2614
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13
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
LDOs have been specifically designed to function with
very low ESR ceramic capacitors. Although the device is
intended to operate with these low ESR capacitors, it is
stable over a very wide range of capacitor ESR, thus it
will also work with some higher ESR tantalum or aluminum electrolytic capacitors. However, for best performance, ceramic capacitors are recommended.
No-Load Stability
The value of COUT typically ranges from 1μF to 10μF;
however, 1μF is sufficient for most operating conditions.
The AAT2614 LDO is designed to maintain output voltage
regulation and stability under operational no-load conditions. This is an important characteristic for applications
where the output current may drop to zero. An output
capacitor is required for stability under no-load operating
conditions. Refer to the Output Capacitor section of this
datasheet for recommended typical output capacitor values.
Enable Function
Internal Power Supply
The AAT2614 features four LDO regulator enable/disable
function for LDO1/2/3/4 respectively. These pins (ENL1,
ENL2, ENL3, and ENL4) are active high and are compatible with CMOS logic. To assure the LDO regulator will
switch on, the EN turn-on control level must be greater
than 2.4V. The LDO regulator will go into the disable
shutdown mode when the voltage on the EN pin falls
below 0.6V. If the enable function is not needed in a
specific application, it may be tied to VIN to keep the LDO
regulator in a continuously on state.
The AAT2614 internal circuitry uses INL1 as the internal
power supply. The buck output OUTB will have no output
when INL1 is not connected to power.
Layout Considerations
The suggested PCB layout for the AAT2614 is shown in
Figures 2(a) - 2(d). The following guidelines are recommended to ensure a proper layout:
1.
Short-circuit and Thermal Protection
The AAT2614 LDOs are protected by both current-limiting
and over-temperature protection circuitry. The internal
short-circuit current limiting circuit is designed to activate
when the output load demand exceeds the maximum
rated output. If a short-circuit condition were to continually draw more than the current limit threshold, the LDO
regulator’s output voltage would drop to a level necessary
to supply the current demanded by the load. Under shortcircuit or other over-current operating conditions, the
output voltage would drop and the AAT2614’s die temperature would rapidly increase. Once the regulator’s
power dissipation capacity has been exceeded and the
internal die temperature reaches approximately 140°C,
the system thermal protection circuit will become active.
The internal thermal protection circuit will actively turn off
the LDO regulator output pass device to prevent the possibility of over-temperature damage. The LDO regulator
output will remain in a shutdown state until the internal
die temperature falls back below the 140°C trip point.
The interaction between the short-circuit and thermal
protection systems allows the LDO regulator to withstand indefinite short-circuit conditions without sustaining permanent damage.
2.
3.
4.
5.
6.
7.
14
Connect the input capacitors (C1, C2, C3) and output capacitors (C4, C5, C6, C7, C8 ) as close as possible to the pins (VIN, VOUT) and power ground
(PGND) to minimize any parasitic inductance in the
switched current path which generates a large voltage spike during the switching interval.
Keep the power traces (GND, LX, and INB) short,
direct, and wide to allow large current flow. Place
sufficient multiple-layer pads when needed to change
the trace layer.
Connect the output capacitor C8 and inductor L1 as
close as possible to the device. Keep the connection
of L1 to the LX pins as short as possible and route
no signal lines under the inductor.
Separate the feedback traces or OUTB pins (Pin 9)
from any power trace and connect as close as possible
to the load point. Sensing along a high-current load
trace will degrade DC load regulation.
Keep the resistance of the trace from the load
returns to PGND to a minimum. This will help to
minimize any error in DC regulation due to differences in the potential of the internal signal ground
and the power ground.
Connect the ground pin of the exposed pad to AGND
internal plane with multiple vias to decrease the
effect of large power ground PGND noise on the analog ground.
Connect the ground pins of LDO output capacitors to
AGND.
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DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
U1
AAT2614IDG-2
1
VIN
2.5V to 5.5V
19
INL1
LDO1
1.8V 300mA
OUTL1
C1
2.2μF
C4
1μF
16
20
INL2
LDO2
2.8V 300mA
OUTL2
C5
1μF
C2
2.2μF
4
15
INB
LDO3
2.8V 300mA
OUTL3
C3
10μF
C6
1μF
7
ENB
ENL1
ENL2
ENL3
ENB
14
ENL1
C7
1μF
3
ENL2
11
ENL3
5
LX
12
ENL4
ENL4
LDO4
2.8V 300mA
OUTL4
2
9
L1
OUTB
17
6
AGND
EP
BO1
1.2V 600mA
2.2μH
PGND
C8
10μF
Figure 1: AAT2614IDG-2 Evaluation Board Schematic.
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15
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
a: Top Side
b: Internal Plane 1 (AGND)
c: Internal Plane 2 (PGND)
d: Bottom Side
Figure 2: AAT2614IDG-2 Evaluation Board Layout.
16
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DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
U1
AAT2614IUN-2
VINL1
2.5V to 5.5V
C3
INL1
OUTL1
C4
C1
2.2μF
C4
1μF
A4
INL2
OUTL2
D4
C2
INB
OUTL3
B3
C3
4.7μF
ENL1
ENL2
ENL3
LDO3
2.8V 300mA
C6
1μF
C1
ENB
LDO2
2.8V 300mA
C5
1μF
C2
2.2μF
VINB
2.5V to 5.5V
LDO1
1.8V 300mA
D3
B2
A1
A2
ENL4
ENB
OUTL4
ENL1
LDO4
2.8V 300mA
C7
1μF
ENL2
ENL3
LX
ENL4
OUTB
B4
A3
AGND
PGND
D2
B1
L1
BO1
1.2V 600mA
2.2μH
D1
C8
10μF
Figure 3: AAT2614IUN-2 Evaluation Board Schematic.
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17
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
a: Top Side
b: Internal Plane 1
c: Internal Plane 2
d: Bottom Side
Figure 4: AAT2614IUN-2 Evaluation Board Layout.
18
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DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Component
Part Number
Description
Manufacturer
U1
C1, C2
C3,C8
C4, C5, C6, C7
L1
AAT2614IDG-2/IUN-2
GRM188R71A225KE15
GRM188R60J106ME47
GRM188R70J105KA12
LQH3NPN2R2MM0
Step-Down DC/DC Converter with Quad High PSRR LDOs
Cap Ceramic 2.2μF 0603 X7R 10V 10%
Cap Ceramic 10μF 0603 X5R 6.3V 10%
Cap Ceramic 1μF 0603 X7R 6.3V 10%
2.2μH, 73mΩ, 1.25A, 20%
Skyworks
Murata
Table 1: AAT2614IDG-2/IUN-2 Evaluation Board Bill of Materials (BOM).
Manufacturer
Murata
Coilcraft
Part Number
L (μH)
Max DCR (mΩ)
Saturation Current (A)
LQH3NP1R5NG0
LQH3NP2R2NG0
LQH3NP3R3NG0
LQH3NP4R7NG0
LPA3015-152MLC
LPA3015-222MLC
LPA3015-332MLC
LPA3015-472MLC
1.5
2.2
3.3
4.7
1.5
2.2
3.3
4.7
100
140
180
260
100
110
130
200
1.47
1.27
0.85
0.8
1.3
1.1
1.1
0.9
Size WxLxH (mm)
3.0x3.0x0.9
3.1x3.1x1.5
Table 2: Surface Mount Inductors.
Manufacturer
Murata
AVX
KEMET
Part Number
Value (μF)
Voltage (V)
Tolerance
Temp.
Co.
Case
GRM188R70J105K
GRM188R70J106K
GRM188R71A225K
GRM188R71A475K
06036C105KAT
06036C106KAT
0603ZC225KAT
0603ZC475KAT
C0603C105K9RAC
C0603C106K9RAC
C0603C225K8RAC
C0603C475K8RAC
1
10
2.2
4.7
1
10
2.2
4.7
1
10
2.2
4.7
6.3
6.3
10
10
6.3
6.3
10
10
6.3
6.3
10
10
10%
10%
10%
10%
10%
10%
10%
10%
10%
10%
10%
10%
X7R
X7R
X7R
X7R
X7R
X7R
X7R
X7R
X7R
X7R
X7R
X7R
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
0603
Table 3: Surface Mount Capacitors.
*Default option.
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19
DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
Ordering Information
DC-DC StepDown (V)
LDO1
(V)
LDO2
(V)
LDO3
(V)
LDO4
(V)
Part Marking1
Part Number (Tape and Reel)2
1
1.2
1.3
1.3
1.3
1.2
1.2
1
1.8
1.8
1.8
1.8
2.8
1.8
2.6
2.8
2.8
2.8
2.8
2.8
2.8
3.0
2.8
2.8
2.8
2.8
1.8
2.8
3.3
2.8
2.8
3.0
3.3
1.8
3.0
L2AYW
H3AYW
L4AYW
L6AYW
L8AYW
M2AYW
M4AYW
AAT2614IDG-1-T1
AAT2614IDG-2-T1
AAT2614IDG-3-T1
AAT2614IDG-4-T1
AAT2614IDG-5-T1
AAT2614IDG-6-T1
AAT2614IDG-7-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
TQFN33-203
3.00 ± 0.05
1.700 ± 0.050
Index Area
0.400 BSC
1.700 ± 0.050
Detail "A"
0.400 ± 0.050
3.00 ± 0.05
R(5x)
Top View
(Saw Type)
Bottom View
0.210 ± 0.040
0.75 ± 0.05
Detail "A"
0
+ 0.10
-0.00
0.203 REF
Side View
(Saw Type)
All dimensions in millimeters.
1. A = assembly house code, Y = year, W = week.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
20
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DATA SHEET
AAT2614
Step-Down DC/DC Converter with Quad High PSRR LDOs
WLCSP-16
0.300
0.100
0.100
Line 2
Top View
0.620 ± 0.085
0.205 ± 0.025
0.300
0.400 BSC
0.200 BSC
1.200 BSC
1.645 ± 0.035
0.170 ± 0.025
0.380 ± 0.025
0.070 ± 0.035
Line 1
Bottom View
Side View
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21